DEpends on the nutes, and what your mix is.
The general rule is that unless a nute system was SPECIFICALLY designed to be mixed in a reservoir for later use, use it IMMEDIATELY.
Try doing the calculations to got numbers for smaller mix volumes. A plastic syringe, turkey baster, or eyedropper with mL marks is very useful in making smaller volume dilutions. You can find them at the pharmacy or cooking gadget store. I use a 'flavor injector' with the needle removed and replaced by a piece of airline hose to measure small volumes of nute solutions.